package com.specter.utils;

import java.io.ByteArrayOutputStream;
import java.nio.charset.StandardCharsets;
import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Signature;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.Base64;
import java.util.HashMap;
import java.util.Map;

import javax.crypto.Cipher;

public class RSAUtils {

    private RSAUtils() {
    }

    /** 加密算法RSA */
    public static final String KEY_ALGORITHM = "RSA";
    /** 签名算法 */
    public static final String SIGNATURE_ALGORITHM = "MD5withRSA";
    /** 获取公钥的key */
    private static final String PUBLIC_KEY = "RSAPublicKey";
    /** 获取私钥的key */
    private static final String PRIVATE_KEY = "RSAPrivateKey";
    /** RSA最大加密明文大小 */
    private static final int MAX_ENCRYPT_BLOCK = 117;
    /** RSA最大解密密文大小 */
    private static final int MAX_DECRYPT_BLOCK = 128;

    /**
     * 生成密钥对(公钥和私钥)
     * 
     * @return 密钥对
     * @throws Exception 错误异常
     */
    public static Map<String, Object> keypair() {
        try {
            KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(KEY_ALGORITHM);
            keyPairGen.initialize(2048);
            KeyPair keyPair = keyPairGen.generateKeyPair();
            RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
            RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
            Map<String, Object> keyMap = new HashMap<>(2);
            keyMap.put(PUBLIC_KEY, publicKey);
            keyMap.put(PRIVATE_KEY, privateKey);
            return keyMap;
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    /**
     * 用私钥对信息生成数字签名
     *
     * @param content    已加密数据
     * @param privateKey 私钥(Base64编码)
     *
     * @return 数字签名
     * @throws Exception 错误异常
     */
    public static String sign(String content, String privateKey) {
        try {
            byte[] keyBytes = Base64.getDecoder().decode(privateKey);
            byte[] data = content.getBytes(StandardCharsets.UTF_8);
            PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
            KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
            PrivateKey privateK = keyFactory.generatePrivate(pkcs8KeySpec);
            Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
            signature.initSign(privateK);
            signature.update(data);
            return encryptBase64(signature.sign());
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    /**
     * 校验数字签名
     *
     * @param content   已加密数据
     * @param publicKey 公钥(Base64编码)
     * @param sign      数字签名
     *
     * @return 校验数字签名
     * @throws Exception 错误异常
     *
     */
    public static boolean verify(String content, String publicKey, String sign) {

        try {
            byte[] keyBytes = Base64.getDecoder().decode(publicKey);
            byte[] data = content.getBytes(StandardCharsets.UTF_8);
            X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
            KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
            PublicKey publicK = keyFactory.generatePublic(keySpec);
            Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
            signature.initVerify(publicK);
            signature.update(data);
            return signature.verify(Base64.getDecoder().decode(sign));
        } catch (Exception e) {
            e.printStackTrace();
            return false;
        }
    }

    /**
     * 私钥解密
     *
     * @param content    已加密数据
     * @param privateKey 私钥(Base64编码)
     * @return 私钥解密
     * @throws Exception 错误异常
     */
    public static String decryptByPrivateKey(String content, String privateKey) {
        try {
            byte[] keyBytes = Base64.getDecoder().decode(privateKey);
            byte[] encryptedData = decryptBase64(content);
            PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
            KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
            Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
            Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
            cipher.init(Cipher.DECRYPT_MODE, privateK);
            int inputLen = encryptedData.length;
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            int offSet = 0;
            byte[] cache;
            int i = 0;
            // 对数据分段解密
            while (inputLen - offSet > 0) {
                if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
                    cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
                } else {
                    cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
                }
                out.write(cache, 0, cache.length);
                i++;
                offSet = i * MAX_DECRYPT_BLOCK;
            }
            byte[] decryptedData = out.toByteArray();
            out.close();
            return new String(decryptedData, StandardCharsets.UTF_8);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    /**
     * 公钥解密
     *
     * @param content   已加密数据
     * @param publicKey 公钥(Base64编码)
     * @return 公钥解密
     * @throws Exception 错误异常
     */
    public static String decryptByPublicKey(String content, String publicKey) {
        try {
            byte[] keyBytes = Base64.getDecoder().decode(publicKey);
            byte[] encryptedData = decryptBase64(content);
            X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
            KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
            Key publicK = keyFactory.generatePublic(x509KeySpec);
            Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
            cipher.init(Cipher.DECRYPT_MODE, publicK);
            int inputLen = encryptedData.length;
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            int offSet = 0;
            byte[] cache;
            int i = 0;
            // 对数据分段解密
            while (inputLen - offSet > 0) {
                if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
                    cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
                } else {
                    cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
                }
                out.write(cache, 0, cache.length);
                i++;
                offSet = i * MAX_DECRYPT_BLOCK;
            }
            byte[] decryptedData = out.toByteArray();
            out.close();
            return new String(decryptedData, StandardCharsets.UTF_8);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    /**
     * 公钥加密
     *
     * @param content   源数据
     * @param publicKey 公钥(Base64编码)
     * @return 公钥加密
     * @throws Exception 错误异常
     */
    public static String encryptByPublicKey(String content, String publicKey) {
        try {
            byte[] keyBytes = Base64.getDecoder().decode(publicKey);
            byte[] data = content.getBytes(StandardCharsets.UTF_8);
            X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
            KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
            Key publicK = keyFactory.generatePublic(x509KeySpec);
            // 对数据加密
            Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
            cipher.init(Cipher.ENCRYPT_MODE, publicK);
            int inputLen = data.length;
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            int offSet = 0;
            byte[] cache;
            int i = 0;
            // 对数据分段加密
            while (inputLen - offSet > 0) {
                if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
                    cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
                } else {
                    cache = cipher.doFinal(data, offSet, inputLen - offSet);
                }
                out.write(cache, 0, cache.length);
                i++;
                offSet = i * MAX_ENCRYPT_BLOCK;
            }
            byte[] encryptedData = out.toByteArray();
            out.close();
            // Base64加密
            return encryptBase64(encryptedData);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    /**
     * 私钥加密
     *
     * @param content    源数据
     * @param privateKey 私钥(Base64编码)
     * @return 私钥加密
     * @throws Exception 错误异常
     */
    public static String encryptByPrivateKey(String content, String privateKey) {
        try {
            byte[] keyBytes = Base64.getDecoder().decode(privateKey);
            byte[] data = content.getBytes(StandardCharsets.UTF_8);
            PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
            KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
            Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
            Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
            cipher.init(Cipher.ENCRYPT_MODE, privateK);
            int inputLen = data.length;
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            int offSet = 0;
            byte[] cache;
            int i = 0;
            // 对数据分段加密
            while (inputLen - offSet > 0) {
                if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
                    cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
                } else {
                    cache = cipher.doFinal(data, offSet, inputLen - offSet);
                }
                out.write(cache, 0, cache.length);
                i++;
                offSet = i * MAX_ENCRYPT_BLOCK;
            }
            byte[] encryptedData = out.toByteArray();
            out.close();

            // Base64加密
            return encryptBase64(encryptedData);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    /**
     * 获取私钥
     *
     * @param keyMap 密钥对
     * @return 获取私钥
     */
    public static String getPrivateKey(Map<String, Object> keyMap) {
        Key key = (Key) keyMap.get(PRIVATE_KEY);
        return new String(Base64.getEncoder().encode(key.getEncoded()));
    }

    /**
     * 获取公钥
     *
     * @param keyMap 密钥对
     * @return 获取公钥
     */
    public static String getPublicKey(Map<String, Object> keyMap) {
        Key key = (Key) keyMap.get(PUBLIC_KEY);
        return new String(Base64.getEncoder().encode(key.getEncoded()));
    }

    /**
     * BASE64解密
     *
     * @param key 秘钥串
     * @return BASE64解密
     */
    public static byte[] decryptBase64(String key) {
        return Base64.getDecoder().decode(key);
    }

    /**
     * BASE64加密
     *
     * @param key 秘钥串
     * @return BASE64加密
     */
    public static String encryptBase64(byte[] key) {
        return new String(Base64.getEncoder().encode(key));
    }

}